Treatment of metal



Patented July 7, 1931 STAVTES PATENT OFFICE FRED J'. CROLIUS AND RUDOLPH W. STULER, PITTSBURGH, PENNSYLVANIA, AS-. SIG-NORS TO STAINLESS STEEL CORPORATION, A CORPORATION OF DELAWARE TREATMENT OF METAL No Drawing.

with a sudden shock or mechanical disturb-- ance to obtain especial benefits in the characteristics of the final product when cast or cooled. It has been proposed to procure this sudden shock by chemical means, that is an explosive material introduced into the bath of the molten metal.

It is the purpose of the present invention to produce a sudden shock or a series of sudden shocks in a bath of molten metal and thus produce all of the benefits incident thereto without the injection of any explosive or other chemicals into the metal. Among other things this eliminates the possibility of there being any remnant of the explosive in the final product. Since gene'rallfthere is no desirability of having any portion of the explosive material remain in the metal its complete exclusion is desirable. Indeed, it may be that the presence of the explosive material is undesirable and deleterious in the final product. i

It has been found that an improved product may be prod?ed by giving to the molten metal by electric means a shock suflicient to produce the desired results. This shocks but avoids a real explosion and so avoids the possibility of accidents due to high pressuresor to spattering or distribution ofhot metal outside its container. A

When it is desired to carry out the present invention iron, steel or alloys thereof may be produced in the usual way in the usual furnaces and then the molten metal may be introduced into an electric furnace and the shock produced by suddenly turning on the full current to afiect the metal bath in the furnace.

It may be more desirable, however, to carry out the manufacture of the metal or at least its alloying in an electric furnace and pro duce the desired shock by turning off the current and. allowing the metal to become quiescent and then suddenly turning on the current to produce the shock. This may be safely done either in a closed or an open furnace without the liability of throwing out Application filed November 12, 1930. Serial No. 495,282.

the metal as might occur if there were an internal explosion.

To the carrying out of the present inven- -t1on is especially adapted the Ajax type of crucible high frequency electric furnace, sometimes referred to as a coreless electric furnace. A ladle type Ajax furnace may be employed to bring a melt of approximately 300 pounds of alloy steel to nearly the final addition point. For instance the carbon steel will be melted, the lime slag Will have boiled, risen, and the manganese may have been added and the heat apparently completed or made. The temperature at this point may be approximately 2850 F. The current in the furnace is abruptly out OK. Then cur rent is suddenly turned on and the full force of say 150 kw. of alternatin current is ressed into the furnace at a frequency of etween 1000 and 2000 cycles. Incidentally the mass is agitated and boils, with increasin temperature and violently increased circu ation.

Every indication of severe shock is observed. Slag previously occluded is freed and rapidly agglomerates on the surface.

Gases are freely and profusely liberated. The metal becomes remarkably fluid and When cast into ingots shows a denser structure and a better surface than corresponding alloys poured when made and not submitted to the shock. istics continue throughout the rolling or other treatment of the metal into its desired finished shape.

Sometimes it is desirable after turning off the current to add to the molten batch further sla beneficiators or further alloying materia s or both. This generally should be done While the current is turned off and before the mass is given the shock by suddenly turnlng on the current.

The procedure indicated produces good results but it may be desirable to submit the metal to a succession of shocks in which event the steps of shutting 0d the current and again suddenly turning on the current may berepeated a suitable number of times.

These beneficial character The details here indicatedare not essential to the invention and those versed in the art I will understand that it may be applied in other ways and be employed as a step in the manufacture of various steels, irons and alloys. The other steps of such manufacture may be adopted, adjusted and varied to suit the needs or desires of the operator.

We claim as our invention:

1. The process of preparing metal in high frequency electric furnaces which comprlses.

subjecting a molten bath of the metal to a sudden shock by suddenly turning into the furnace the full force of the alternating cur-. rent.

2. The process of preparing metal comprising melting and treating it in a high frequency electric furnace, shutting off the electric current, and turning on the electric current to give a sudden shock to the metal.

3. The process of preparing metal comprising heating the metal in a high frequency electric furnace to the final addition point at about 2850 F., turning off the current, suddenly turning on a current of 150 kw. with a frequency of between 1000 and 2000 cycles.

4. The process of preparing metal comprising heating the metal in a high frequency elec tric furnace to the final addition point, shutting off the current, adding elements desired, and suddenly shocking the metal by turning on the current.

5. The step in preparing metals compris ing shocking a molten bath of the metal in a high frequency electric furnace by suddenly subjecting it to sufi'icient electric current to shock the bath.

6. The step in preparing metal comprising repeatedly shocking a molten bath of the metal in a high frequency electric furnace by repeatedly suddenly subjecting it to sulficient electric current to shock the bath.

7. The process of preparing metal comprising heating the metal in a high frequency electric furnace to the final addition point,

7 shutting off the current, adding elements desired, and suddenly subjecting it to a sufficient electric current to shock the bath a plurality of times.

, F. J. CROLIUSV V RUDOLPH W; STULER. 

